Ground State Of CO Research Articles

The 1992 Evaluation of Mass-Independent Dunham Parameters for the Ground State of CO

The 1992 Evaluation of Mass-Independent Dunham Parameters for the Ground State of CO

Fundamental studies of the energetics and dynamics of state-selected cobalt(+) reacting with methyl iodide. The Co+-CH3 and Co+-I bond energies

The a 3 F, a 5 F, and b 3 F states of Co + react with CH 3 I to form the CoCH 3 I + adduct as well as CoCH 3 + +I and CoI + +CH 3 products. The observed rates for adduct formation and methyl elimination were found to be strongly dependent on the electronic configuration of the metal ion. Under our experimental conditions (10 -5 Torr of CH 3 I in 1.15 Torr of He), adduct formation is the dominant product for the a 3 F 3d 8 ground state of Co + , with only small amounts of elimination products observed

Infrared spectroscopy of CO2–D(H)Br: Molecular structure and its reliability

A high resolution rovibrational absorption spectrum of the weakly bonded CO2–DBr complex has been recorded in the 2350 cm−1 region by exciting the CO2 asymmetric stretch vibration with a tunable diode laser. The CO2–DBr band origin associated with this mode is 2348.2710 cm−1, red-shifted by 0.87 cm−1 from uncomplexed CO2. The position of the hydrogen atom is determined from differences in moments-of-inertia between CO2–DBr and CO2–HBr, i.e., by using the Kraitchman method. From this, we conclude that ground state CO2–H(D)Br has an average geometry that is planar and inertially T-shaped, with essentially parallel HBr and CO2 axes. Average values of intermolecular parameters are: Rcm=3.58 Å, θBrCO=79.8°, and θHBrC=93.1°. The validity of using the Kraitchman method, which was designed for use with rigid molecules, with a floppy complex like CO2–HBr is discussed. The experimental structure is corroborated qualitatively by results from Mo/ller–Plesset second-order perturbation calculations, corrected for basis set superposition errors. The theoretical equilibrium geometry for the inertially T-shaped complex is planar with structural parameters: RCBr=3.62 Å, θBrCO=89°, and θHBrC=86°. A number of cuts on the four dimensional intermolecular potential surface confirm large zero-point amplitudes, which are known to be characteristic of such systems, and these cuts are used to estimate tunneling splittings. Tunneling is shown to occur by out-of-plane rotation of the H atom, in accord with the experimental observations of Rice et al. There is no significant in-plane tunneling. A quasilinear hingelike isomer (OCO–HBr) with ROH=2.35 Å at equilibrium is calculated to be as stable as the T-shaped complex; however, this species has yet to be observed experimentally. Photoinitiated reactions in CO2–HX complexes are discussed.

A variation perturbation calculation of pseudostates and polarizabilities for CO and NO

Molecular pseudostates, needed to describe the induced polarization in electron-molecule scattering, are computed by a variation perturbation method. Polarizabilities are obtained as a by-product. The emphasis is put on the definition of an optimal atomic basis set: a new procedure for generating the polarization functions required to complement a standard basis is presented, tested, and discussed. The method is applied to the ground states of CO and NO. The resulting polarizabilities are within 10% of the experimental values, in accordance with the neglect of correlation in the unperturbed state.

First results from Goddard High-Resolution Spectrograph - C I, S I, and CO toward XI Persei and the physical conditions in diffuse clouds

view Abstract Citations (31) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS First Results from the Goddard High-Resolution Spectrograph: C i, S i, and CO toward XI Persei and the Physical Conditions in Diffuse Clouds Smith, Andrew M. ; Bruhweiler, Frederick C. ; Lambert, David L. ; Savage, Blair D. ; Cardelli, Jason A. ; Ebbets, Dennis C. ; Lyu, Cheng-Hsuan ; Sheffer, Yaron Abstract Observations made by the Goddard High Resolution Spectrograph of the cool, neutral interstellar gas in the line of sight to Xi Per are reported. Heliocentric velocities and equivalent widths were measured for absorption lines of C I and S I. Synthetic spectra were computed and fitted to the observed CO(2-0) and (3-0) bands in the A IPi - X 1Sigma(+) system. Derived populations of the C I ground-state fine-structure levels and the CO ground-state rotational levels were used to derive densities of two of the three, and possibly four, detected cloud components. The velocity component displaying the strongest C I absorption reveals extraordinarily high pressure. Publication: The Astrophysical Journal Pub Date: August 1991 DOI: 10.1086/186117 Bibcode: 1991ApJ...377L..61S Keywords: Carbon; Carbon Monoxide; Hubble Space Telescope; Interstellar Gas; Molecular Clouds; O Stars; Spectrographs; Sulfur; High Resolution; Interstellar Matter; Ultraviolet Spectra; Astrophysics; INTERSTELLAR: MATTER; INTERSTELLAR: MOLECULES; ULTRAVIOLET: SPECTRA full text sources ADS | data products SIMBAD (3) MAST (1) ESA (1)

Theoretical potential energy function and rovibronic spectrum of CO+2(X 2Πg)

For the electronic ground state of CO+2 the three-dimensional potential energy, electric dipole, and transition moment functions have been calculated from highly correlated multireference configuration interaction electronic wave functions. Along the antisymmetric stretching displacements the shape of the potential energy functions is found to be very sensitive to the electron correlation effect. Using a modified theoretical potential energy function rovibronic energy levels have been calculated variationally by the method of Carter and Handy. In this approach, anharmonicity, rotation–vibration, electronic angular momenta, and electron spin coupling effects have been accounted for. The vibronic band origins agree to within about 10 to 20 cm−1 with the available experimental data, and the rotational levels agree to within 0.01 cm−1 for low J values. Additional vibrational band origins have been predicted for energies up to 3200 cm−1. The anomalously low frequency of the antisymmetric stretching mode and its inverse anharmonicity in the X 2Πg state of CO+2 have been reproduced with the potential energy functions for the adiabatic states. Previously, it has been assumed that this effect is due to the vibronic coupling. The molecular parameters of one-dimensional effective Hamiltonians obtained from fits of the spectral data are compared with those derived from the theoretical potential.

Revised molecular constants for the ground state of CO

The Dunham parameters of the ground state of the CO molecule are determined by a least squares fit of recent high-quality microwave and heterodyne frequency measurements. It is shown that these new parameters are more accurate than others obtained recently. Revised equilibrium molecular constants have been deduced from these new Dunham parameters and the mass-scaling coefficients determined by Guelachvili et al. The most important constants are ωe = 65 047 645(7) MHz, ωe x e = 398 365·1(14) MHz, ωe y e = 312·11(14) MHz, B e = 57 907·98(6) MHz, αe = 524·791(13) MHz, D e = 0·183 520 8(57) MHz and R e = 1·128 243(1) Å. The new ground state parameters allow precise determination of the transition frequencies, which can now be used as secondary standards in the microwave and infrared ranges.

Photodissociation of CO−3: Product kinetic energy measurements as a probe of excited state potential surfaces and dissociation dynamics

The photodissociation process CO−3 +hν→O−+CO2 has been investigated at photon energies of 2.41, 2.50, 2.54, 2.60, and 2.71 eV. Experiments were conducted by crossing a mass-selected, 8 keV ion beam with a linearly polarized laser beam, and measuring the kinetic energy distributions of the charged photodissociation products. By varying the angle between the ion beam and laser polarization, angular distributions were obtained at photon energies of 2.41 and 2.54 eV. The photon energy dependence of the average photofragment kinetic energies shows conclusively that photodissociation at these photon energies does not proceed by a direct dissociation process on a repulsive potential surface, or by a statistical vibrational predissociation process on a bound surface. The photofragment angular distributions are isotropic, providing further evidence that precludes direct photodissociation on a repulsive potential surface. Ab initio calculations were performed using the gaussian86 programs. These calculations indicate that ground state CO−3 has a planar D3h geometry, and 2A′2 electronic symmetry. This ground state correlates adiabatically to the CO−2 +O dissociation asymptote, not the lower energy O−+CO2 asymptote. Taken together, these new experimental and theoretical results suggest that the photodissociation of CO−3 at these energies occurs via the interaction of bound and repulsive excited state potential surfaces. A new model of the potential surfaces of CO−3 is proposed.

Theoretical studies of the transition metal–carbonyl systems MCO and M(CO)2, M=Ti, Sc, and V

A b initio calculations on the transition metal–carbonyl systems MCO and M(CO)2, M=Ti, Sc, and V, have been carried out using large Gaussian basis sets and an extensive treatment of electron correlation. The dissociation energies (De) and geometries of these molecules are given, and the bonding mechanisms are discussed. High-spin ground states are favored for the monocarbonyl molecules, whereas for the dicarbonyl molecules there is a competition between high-, intermediate-, and low-spin states, which are found to be very close in energy. The computed De(Ti–CO) is 0.62 eV whereas for Ti(CO)2 it is 1.02 eV, relative to the ground state Ti atomic asymptote and CO(1Σ+). This suggests that the recent experiment giving a value of ≊1.75 eV for De[Ti–(CO)x] should be interpreted as giving the De for Ti(CO)x, x≥2. For the three metal atoms the binding energy per carbonyl is found to be significantly lower for the dicarbonyl than the monocarbonyl molecules. This is in contrast to the Ni(CO)x molecules, where each CO is bound with approximately the same energy.

Radiation-induced perturbations in C2 and CH sidelight in the CO-He-Xe laser

Visible C2 and CH sidelight emission in a CO-He-Xe laser discharge exhibits intensity fluctuations of typically 30-40% when laser oscillation is chopped on and off. Chemical reactions in the discharge plasma are shown to play the major role in the perturbations of the C2 Swan and high-pressure bands and the CH 4300 AA bands. The dissociation of CO is shown to take place in the reaction of CO (a 3 Pi r) metastables and ground-state CO, and via the reaction of two vibrationally excited ground-state CO molecules, rather than via direct electron impact.

Vibrational-rotational energy levels of diatomic molecules from the hill determinant method

The Hill determinant method is applied to the perturbed-Morse-oscillator model. Accurate vibrational-rotational energies are obtained for the ground state of CO.

Angular dependence of vibronic excitation in He++CO, N2collisions at medium energies: evidence for non-Franck-Condon and non-Poisson vibrational distributions

The vibrational populations of CO(X 1 Sigma + and a 3 Pi ) and N2(X 1 Sigma g+ and B 3 Pi g) produced in collisions of He+ with CO(X) and N2(X) in the E=100-1000 eV energy range are studied, using a high-resolution energy loss spectrometer, as a function of the scattering angle theta of the He+ particles. The results for CO(a 3 Pi ) show dramatic deviations from the Franck-Condon distribution and exhibit contrasting behaviours as a function of both E and theta . The measured vibrational distributions for CO(X) and N2(X) deviate strongly from the often invoked Poisson distribution and show peculiar dependences as functions of E and theta . The possible bond-length-dependent phenomena that could influence the vibronic excitation into CO(a, nu ') are discussed. A simple model is set up to explain the main effects that govern the dependence of the vibrational distribution in the electronic ground states of CO and N2.

Electron scattering from vibrationally excited CO2

The total cross section for electron scattering from vibrationally excited (principally 010) CO2 molecules has been measured in the energy range 0.12-2.0 eV with a time of flight electron spectrometer. The vibrationally excited molecules were produced by thermal excitation of the gas contained in a scattering cell at a temperature of 300 degrees C. The cross section for scattering from these excited molecules was deduced by comparison with similar measurements performed at room temperature. At energies below 2 eV the excited-state cross section is considerably larger than that for scattering from ground-state CO2. The ground-state measurements are in excellent agreement with other recent experimental and theoretical work. No other experimental or theoretical data exist for the excited-state cross section.

Selective vibrational excitation and mode conservation in H++CO2/N2O inelastic and charge transfer collisions

Total angular distributions and vibrationally resolved time-of-flight spectra have been measured for H++CO2/N2O at collision energies of 9.8 and 30 eV and scattering angles up to θ=15°. Results are available for the scattered protons as well as for H atoms from charge transfer collisions into the electronic ground states of CO+2/N2O+. For both systems, the H+ and H product channels exhibit practically identical total angular distributions with marked rainbow structures in the CO2 case. The time-of-flight distributions, on the other hand, reveal strongly selective excitation of the ν3 fundamental modes and their overtones for both target molecules and both product channels. In addition, at each scattering angle, the ν3 transition probability distributions for CO2 and N2O are remarkably similar to those for CO+2 and N2O+, respectively. The dominance of the ν3 mode excitation in the neutral molecules is in accord with what is expected from the combination of dipole- and valence-type interaction mechanisms on the lower H++CO2/N2O potential energy surfaces. Excitation of the same mode with nearly the same distributions in the charge transfer channel is explained by Franck–Condon selection rules, which favor transitions between identical vibrational states of either CO2 and CO+2 or N2O and N2O+.

Vibrational analysis of N 2(B 3Π g and C 3Π u) and CO(X) excited in N 2 discharge and post discharge

A spectroscopic characterization of a N 2 radiofrequency discharge and N 2CO post discharge has been performed. The relative vibrational distribution of the excited B 3Π g and C 3Π u states of nitrogen and their correlation with the ground state have been analyzed. The analysis confirms the importance of the metastable molecules. N 2(A 3Σ + u), in affecting the vibrational distribution of nitrogen in its ground state in the discharge and post discharge. The vibrational analysis of the CO ground state, excited in the post discharge by vibrationally excited N 2 molecules, confirms the high degree of vibrational non-equilibrium in the ground state of nitrogen, in the presence of a low first-level vibrational temperature.

The charge transfer reactions of protons with carbon dioxide: A two-state treatment

Although the dissociative electron transfer reactions between protons and carbon dioxide are endothermic by 0.19–9.1 eV, the reactions have a large total cross section at low keV collision energies. The results are quantitatively modelled in terms of the modified Strueckelberg-Demkov mechanism for the non-crossing of reactant and product diabatic potential energy curves. Charge transfer to give the ground state of CO + 2 occurs at 4.05–4.26 Å. The H atom and CO + 2 formed may then suffer a non-crossing excitation at 1.6–2.1 Å during the evolution of a single-collision event, to produce the excited CO + 2. The experimental results cannot be interpreted by a curve crossing mechanism of the Landau-Zener type.

Electronic energy transfer between O2 and CO dopants in Ar crystals

Excitation spectra of Ar crystals doubly doped with O2 and CO show the a 3Π, a′ 3∑+, d 3Δ, e 3∑−, A 1Π vibrational progressions of CO as well as the Schumann Runge bands ( B 3∑−u) and the following dissociation continuum of O2. In emission the Cameron bands (a 3Π) of CO and the Herzberg bands C 3Δu of O2 have been observed. No electronic energy transfer from CO to O2 or vice versa occurs. This rules out an intramolecular V–E conversion of high vibrational quanta (v=32) in the electronic ground state of CO to the a 3Π (v=3) state of CO and subsequent electronic energy transfer to O2 in the recently reported IR-induced UV-visible fluorescence in matrix-isolated CO thus supporting the other suggested intermolecular V–E and V–V transfer routes.

Rotational state distribution of CO photofragments from triplet ketene

The nascent rotational state distribution of CO(v″=0,J″) following excimer laser photolysis of ketene at 351 nm has been determined under collisionless conditions in a flow cell. At this low excitation energy dissociation can only take place on the triplet potential surface leading to CH2(X̃ 3B1) and CO(X̃ 1Σ+). The available energy permits only the vibrational ground state of CO to be populated. The observed rotational distribution of CO(v″=0,J″) deviates drastically from a phase space theory statistical distribution as well as from a thermal one. A Boltzmann plot of this distribution exhibits a population inversion for J″<13. The nonstatistical behavior is attributed to a barrier along the dissociation path. The fragments are repelled too rapidly for energy to be randomized between them. Thus the photofragmentation dynamics of triplet ketene contrasts markedly with dissociation on the singlet surface which has no barrier and gives a statistical CO rotational state distribution. An impulsive model calculation for the ab initio transition state geometry is in surprisingly good agreement with the experimental energy partitioning among the fragment degrees of freedom. This suggests that the CCO bond angle is strongly bent at the top of the barrier and that the barrier height is a substantial fraction of available energy.

Collision complex formation in the low-energy dynamics of the C + + O 2 reaction

A crossed beam study of CO + production from the C + + O 2 reaction at a collision energy of 0.57 eV is presented. Very clear collision complex dynamics are observed which are shown to be consistent with the decay of a transient complex having a lifetime of approximately 0.5 ps. An analysis of the reactive scattering using an adiabatic state correlation diagram indicates that the formation of X-state CO 2 + by insertion of C + into the O 2 bond is accessible from the reagents and correlates adiabatically with ground-state products. The average kinetic energy release is approximately 23% of the available energy. A comparison of the present data with the chemiluminescent studies of A-state production of CO + indicates that the dominant channels at low energies are production of ground-state CO + through the X 2Π g and a 4Π u state of CO 2 +.

Dissociation on ground-state potential-energy surfaces

Two new techniques allowing for the resolved spectral study of dissociation on ground-state potential-energy surfaces are presented. First, Stark level-crossing spectra of highly vibrationally excited ground-state formaldehyde (S*0) characterize the initial rovibrational wavefunctions of dissociative formaldehyde states. Individual S*0 D2CO states are resolved near the barrier to dissociation but broaden and overlap at higher energies. Neighbouring resolvable states possess enough individual vibrational character to vary by over one order of magnitude in lifetime. A potential barrier height of 78.0–81.1 kcal mol–1 has been determined for H2CO → H2+ CO dissociation. Second, photofragment excitation (PHOFEX) spectra probe the production of correlated fragment states from ketene photodissociation. Molecular-beam PHOFEX spectra show that ketene possesses no observable rotational structure and only weak vibrational structure. The PHOFEX spectrum of an individual rotational state of the lowest vibronic state of singlet methylene gives the energetic threshold for formation of that state along with ground-state CO. The threshold for the combination with each successive CO(v″= 0, J″) channel is clearly resolved. A statistical calculation reproduces the main features of the PHOFEX spectra. Analysis of the PHOFEX spectra gives a H2CCO →1CH2+ CO dissociation threshold of 30 102 ± 15 cm–1. Finally, the effect of a potential barrier in the dissociation coordinate on statistical vs. dynamical control of dissociation is discussed.